Cyclophilin–calcineurin interface (None established; the interface itself does not commonly have an abbreviation, but components are: - Cyclophilin A (CyPA) - Calcineurin (CN))

The cyclophilin-calcineurin interface is the molecular interaction site where the cyclophilin A–cyclosporin A complex binds calcineurin, leading to inhibition of calcineurin’s serine/threonine phosphatase activity. This functional blockade disrupts dephosphorylation of transcription factors like NFAT, suppressing T cell activation and immune responses. The interaction is the molecular basis for the immunosuppressive effects of cyclosporin A and related therapies. Although this interface is crucial for drug mechanism, it is not a standalone molecular entity or a receptor, but a composite binding surface formed by both the catalytic and regulatory subunits of calcineurin. Structural studies highlight distinct contact residues for cyclophilin–CsA versus other immunophilin complexes, underpinning drug specificity and selectivity.

Other names

Cyclophilin–calcineurin interaction siteCyclophilin A–calcineurin binding surfaceCyPA–CN interface

Cyclosporin A binds cyclophilin to form a complex. Cyclophilin–CsA complex binds the interface on calcineurin. This binding inhibits calcineurin's phosphatase activity, suppressing T cell activation by preventing dephosphorylation and nuclear translocation of NFAT (nuclear factor of activated T cells).